feat: (feature/dynamodb/expression) re-add IsSet methods (#1329)

* feat: (feature/dynamodb/expression) readd IsSet methods

These changes were present in an older version of the expression package before it was moved, originally added in #494, when the expression library was reintroduce in #981 these changes werent included for some reason, but the need for checking if a condition is set or not still exists

* Add Change Annotation

Co-authored-by: Sean McGrail <mcgrails@amazon.com>

.changelog/8e261b4b5633485cad821d38e2677e46.json

@@ -0,0 +1,8 @@
+{
+    "id": "8e261b4b-5633-485c-ad82-1d38e2677e46",
+    "type": "feature",
+    "description": "Add IsSet helper for ConditionBuilder and KeyConditionBuilder ([#1329](https://github.com/aws/aws-sdk-go-v2/pull/1329))",
+    "modules": [
+        "feature/dynamodb/expression"
+    ]
+}

feature/dynamodb/expression/condition.go

@@ -88,6 +88,20 @@ type ConditionBuilder struct {
 	mode          conditionMode
 }
 
+// IsSet returns true if the ConditionBuilder is set and returns false
+// otherwise. A zero value of a ConditionBuilder returns false.
+//
+// Example:
+//
+//     var condition expression.ConditionBuilder
+//     condition.IsSet() // returns false
+//
+//     condition := expression.Equal(expression.Name("foo"), expression.Value(5))
+//     condition.IsSet() // returns true
+func (cb ConditionBuilder) IsSet() bool {
+	return cb.mode != unsetCond
+}
+
 // Equal returns a ConditionBuilder representing the equality clause of the two
 // argument OperandBuilders. The resulting ConditionBuilder can be used as a
 // part of other Condition Expressions or as an argument to the WithCondition()

feature/dynamodb/expression/condition_test.go

@@ -21,6 +21,33 @@ const (
 	invalidConditionOperand = "BuildOperand error"
 )
 
+//IsSet
+func TestIsSet(t *testing.T) {
+	cases := []struct {
+		name     string
+		input    ConditionBuilder
+		expected bool
+	}{
+		{
+			name:     "set",
+			input:    Equal(Name("foo"), Value("bar")),
+			expected: true,
+		},
+		{
+			name:     "unset",
+			input:    ConditionBuilder{},
+			expected: false,
+		},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			if actual := c.input.IsSet(); actual != c.expected {
+				t.Errorf("expected %t, got %t", c.expected, actual)
+			}
+		})
+	}
+}
+
 //Compare
 func TestCompare(t *testing.T) {
 	cases := []struct {

feature/dynamodb/expression/key_condition.go

@@ -68,6 +68,20 @@ func KeyEqual(keyBuilder KeyBuilder, valueBuilder ValueBuilder) KeyConditionBuil
 	}
 }
 
+// IsSet returns true if the KeyConditionBuilder is set and returns
+// false otherwise. A zero value of a KeyConditionBuilder returns false.
+//
+// Example:
+//
+//     var keyCondition expression.KeyConditionBuilder
+//     keyCondition.IsSet() // returns false
+//
+//     keyCondition := expression.KeyEqual(expression.Key("foo"), expression.Value(5))
+//     keyCondition.IsSet() // returns true
+func (kcb KeyConditionBuilder) IsSet() bool {
+	return kcb.mode != unsetKeyCond
+}
+
 // Equal returns a KeyConditionBuilder representing the equality clause of
 // the two argument OperandBuilders. The resulting KeyConditionBuilder can be
 // used as a part of other Key Condition Expressions or as an argument to the

feature/dynamodb/expression/key_condition_test.go

@@ -24,6 +24,33 @@ const (
 	invalidKeyConditionFormat = "buildKeyCondition error: invalid key condition constructed"
 )
 
+//IsSet
+func TestKeyIsSet(t *testing.T) {
+	cases := []struct {
+		name     string
+		input    KeyConditionBuilder
+		expected bool
+	}{
+		{
+			name:     "set",
+			input:    KeyEqual(Key("foo"), Value("bar")),
+			expected: true,
+		},
+		{
+			name:     "unset",
+			input:    KeyConditionBuilder{},
+			expected: false,
+		},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			if actual := c.input.IsSet(); actual != c.expected {
+				t.Errorf("expected %t, got %t", c.expected, actual)
+			}
+		})
+	}
+}
+
 func TestKeyCompare(t *testing.T) {
 	cases := []struct {
 		name         string